Hepatitis C is a viral hepatitis developed by infection with hepatitis C virus. Infection with hepatitis C virus sometimes cures inartificially; however, in many cases, it progresses to chronic hepatitis when left unattended. When the state of chronic hepatitis continues, it progresses to cirrhosis, and further, the risk of developing liver cancer increases. There are even reports stating that about 80% of the cause of liver cancer is hepatitis C.
In the treatment of hepatitis C, interferon therapy achieves a certain treatment outcome. Depending on the genotype of hepatitis C virus, however, interferon therapy may be less effective (for example, type 1b high viral load case). Therefore, the development of a treatment method effective for a broader range of patients has been desired.
Virus-infected cells expose, on the surfaces thereof, a major histocompatibility antigen complex (MHC) presenting partial peptide of a viral internal protein. If cytotoxic T lymphocytes (CD8+ T cells, cytotoxic lymphocytes: CTL) capable of specifically killing virus-infected cells exhibiting these features can be induced, the replication, and hence proliferation and spread of the virus, can be prevented effectively.
Hepatitis C virus is known to have low immunogenicity as compared to other viruses. Thus, a method of inducing CTL by utilizing an epitope having comparatively high immunogenicity, which is present in hepatitis C virus antigen, has been considered.
Patent document 1 discloses a peptide derived from the protein of hepatitis C virus, which induces an HLA-restricted CTL response in an immunized host. Patent document 2 discloses an immunogenic peptide of hepatitis C virus capable of binding to HLA A2.1, and an induction method of cytotoxic T lymphocyte by a composition containing the peptide. However, it is unknown whether these peptides are effective for the actual treatment or prophylaxis of hepatitis C.
On the other hand, as a method for potentiating an immune response in the body, a method using a liposome preparation is known.
Patent Document 3 discloses a method of preparing a T cell activator capable of efficiently and specifically augmenting CTL to kill pathogen-infected cells or cancer cells using an antigen-bound liposome, and useful for the prevention or treatment of infectious diseases and cancers.
In addition, patent document 4 describes that an antigen epitope especially effective for the preparation of cytotoxic T lymphocytes was found in a highly conserved internal protein sequence of avian influenza virus, and that a liposome bound, on its surface, with a peptide containing the epitope can extremely strongly induce antigen specific cytotoxic T lymphocytes.